This invention relates to balloon-type catheters or endotracheal tubes designed for insertion into a patient for introduction of gases to the patient. Such catheters are commonly inserted into a patient's trachea, or windpipe, and include an inflatable balloon or cuff at the distal end which, when inflated, retains the catheter in position and seals the catheter against the internal wall of the trachea.
At the present time, it is common commercial practice to provide disposable catheters of the type herein described. Such tubes can be used only once and then disposed of, thus eliminating the cost of sterilizing to prevent cross-infection. The practical value of disposability, of course, depends greatly upon the cost of producing and marketing the disposable tubes. Such tubes, therefore, should be capable of rapid mass production manufacturing techniques, yet the resultant catheter must, of course, be of fool-proof design so that mass production cannot give rise to the possibility of a failure or defect in the catheter.
In the prior art relevant to endotracheal tubes of the foregoing type, it has occasionally been recognized that the said tubes should preferably be designed as to facilitate rather than impede tube insertion. The significance of this problem is noted, for example, in U.S. Pat. No. 3,862,635, which discloses an endotracheal tube so formed as to define a smooth exterior sliding surface at the distal end of the tube carrying the secured cuff, thereby facilitating the said tube insertion. In the foregoing connection it may be noted that it is most important to assure that the inflatable cuff itself presents no impediment to insertion of the tube into a patient's trachea. It has been found, however, that the prior art cuffs can indeed present an inherent impediment, in that in their deflated conditions the random wrinkling and folding of the cuff can provide projecting portions which can impede the insertion of the cuff -- and its subsequent seating against the trachea wall.
In the balloon-type catheters of the present type, the catheter further includes a pilot balloon which is generally joined to the main cuff by a small passageway or lumen and is in series thereto so that the pilot balloon and main cuff inflate and deflate simultaneously. A valve means is provided to control the gas which may be forced into the pilot balloon, and thus, via the lumen, to the main cuff or balloon. The pilot balloon remains exterior of the patient and thus is used as a continuous visual indication as to the inflated or deflated state of the main cuff. This visual indication must be as clear as possible so that there is no doubt to any viewer as to the condition of the main cuff at any time. Present pilot balloons generally are formed in a simple oval shape. Even when the gas pressure within the main cuff is released, a false indication may be gained, in that the pilot balloon appears inflated even when the main cuff is not pressurized. The false indication is attributable to the shape of the pilot balloon or its wall thickness, or both factors.
A further problem in present disposable balloon-type catheters is in the valve itself. The cuff and pilot balloons are preferably inflated by means of a syringe which is inserted into or adjacent the valve and gas is forced from the syringe into the pilot balloon, thence, through the lumen to the main cuff. Various valves are commercially available to serve this purpose. Some are relatively expensive to mass produce in thay they include a plurality of separately manufactured and assembled components while others are not operable by the syringe itself. The disadvantage of the former drawback is economics, while the disadvantage of the latter drawback is that the valves may not operate instantaneous, so that some gas is lost in trying to close off the passageway to the lumen or are cumbersome in actual operation.
In accordance with the forgoing it may be regarded as an object of the present invention to provide a tracheal tube of the type including an inflatable cuff and a pilot balloon, wherein the pilot balloon is so structured as to provide a very positive and highly visual indicator with respect to the condition of inflation of the said cuff.
It is a further object of the present invention, to provide a tracheal tube of the type including an inflatable cuff portion for sealing with the interior of a patient's trachea, wherein the said cuff is so formed as to facilitate insertion of the tube into the patient's trachea, and to facilitate subsequent seating of the cuff with the trachea wall upon cuff expansion.